nm vs nanometer

nm and nanometer both are nouns.

Word	Noun	Adjective	Verb	Adverb
nm	Yes	No	No	No
nanometer	Yes	No	No	No

As nouns, nm and nanometer are synonyms defined as:

Other synonyms of nm include micromillimeter, micromillimetre, millimicron, nanometre.

nm (noun)	nanometer (noun)
a metric unit of length equal to one billionth of a meter	a metric unit of length equal to one billionth of a meter